"Eight Days a Week" is a song by the English rock band the Beatles. It was written by Paul McCartney and John Lennon based on McCartney's original idea. The song was released in the United Kingdom in December 1964 on the album Beatles for Sale. In the United States, it was first issued as a single in February 1965 before appearing on the North American release Beatles VI. The song was the band's seventh number 1 single on the Billboard Hot 100, a run of US chart success achieved in just over a year. The single was also number 1 in Canada, Belgium and the Netherlands.

Beatles for Sale is the fourth studio album by the English rock band the Beatles. It was released on 4 December 1964 in the United Kingdom on EMI's Parlophone label. The album marked a departure from the upbeat tone that had characterised the Beatles' previous work, partly due to the band's exhaustion after a series of tours that had established them as a worldwide phenomenon in 1964. Beatles for Sale was not widely available in the US until 1987, when the Beatles' catalogue was standardised for release on CD. Instead, eight of the album's fourteen tracks appeared on Capitol Records' concurrent release, Beatles '65, issued in North America only.